You can't use cryptocurrency to buy items in the game because of Google and Apple store policies.
BitCrystals are used to buy blockchain cards outside the game via Swapbots directly from EDS or third parties as well as on the Market on Book of Orbs and the Counterparty DEX.
Have Spells of Genisis any plans to launch the game on the mobile go platform, would be great to be able to use your bit crystals to purchase the gems.
That's one for the team, dunno much about MobileGo but I think it's a competitor and EDS is working on their own platform Project Orb/Book of Orbs.
However not for me to say nor judge.
You guys need to read between lines, it will save you a ton of questions. Many bright minds and big-headed nerds are involved in MobileGo, Zimbeck is one of them. Rarely he comments in blackcoin thread since he's fully focused on making contributions to MobileGo App. They have an excess of talented coders and all of them are worthy assets to MobileGo community.